Continuous tube reactor

ABSTRACT

A system and method for digesting cellulosic material to extract fermentable sugars, lignin, and pulp is disclosed. One embodiment comprises a continuous digester comprising a cellulosic material feed section including a pre-steam and impregnation zone, a sugar extraction zone, a lignin extraction zone and a cooking zone, the continuous digester to impregnate the cellulosic material with a mild acid solution and continuously digest the cellulosic material to extract fermentable sugars, lignin, and pulp. Another embodiment comprises a method for receiving cellulosic material in a continuous digester, removing air from the cellulosic material, impregnating the cellulosic material with a mild acid, hydrolyzing hemicellulose in the cellulosic material to fermentable sugars, extracting the fermentable sugars from the cellulosic material, cooking the cellulosic material to extract lignin from the cellulosic material, washing the cellulosic material in a hot alcohol wash, a hot water wash, and a cold water wash, and discharging pulp.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority of U.S. Provisional patentapplication Ser. No. 61/180,067, filed May. 20, 2009.

BACKGROUND

The disclosed embodiments relate generally to the art of cellulosicmaterial digesters, and more particularly to a continuous tube reactorto extract fermentable sugars, lignin and pulp from cellulosic material.

In a typical continuous pulp digester, the wood chips and the whiteliquor are fed into the upper end of a vertically aligned digester, withthe interior of the digester defining a cylindrical digesting chambermaintained at a relatively high pressure (e.g. 200 PSI) and hightemperature (e.g. approximately 380.degree. F.). The mixture of chipsand white liquor moves slowly and downwardly through the digester sothat the total dwell time within the digester is generally between abouttwo to four hours. During the period that the wood chips are in thedigester, the white liquor reacts with the material in the wood chips tobreak down certain organic compounds in the wood chips so as to“delignify” the pulp.

At several locations along the length of the digester, portions of theliquid are extracted, either to be re-circulated back into the digester,sent to an evaporator, or possibly to be processed elsewhere in thesystem. To retain the wood chips that are being processed in thedigester, the liquid is extracted through sets of screens which aregenerally placed in sets at vertical locations circumferentially aroundthe digester.

SUMMARY

Accordingly, a system and method for continuous tube reactor isdisclosed.

One embodiment comprises a continuous digester comprising a cellulosicmaterial feed section including a pre-steam and impregnation zone, asugar extraction zone, a lignin extraction zone and a cooking zone, thecontinuous digester to impregnate the cellulosic material with a mildacid solution and continuously digest the cellulosic material to extractfermentable sugars, lignin, and pulp. Another embodiment comprises amethod for receiving cellulosic material in a continuous digester,removing air from the cellulosic material, impregnating the cellulosicmaterial with a mild acid, hydrolyzing hemicellulose in the cellulosicmaterial to fermentable sugars, extracting the fermentable sugars fromthe cellulosic material, cooking the cellulosic material to extractlignin from the cellulosic material, washing the cellulosic material ina hot alcohol wash, a hot water wash, and a cold water wash, anddischarging pulp.

This Summary is provided to introduce concepts in a simplified form thatare further described below in the Detailed Description. This Summary isnot intended to identify key features or essential features of theclaimed subject matter, nor is it intended to be used to limit the scopeof the claimed subject matter. Furthermore, the claimed subject matteris not limited to implementations that solve any or all disadvantagesnoted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an isometric view of one form of a digester.

FIG. 2 shows a schematic view of a continuous tube reactor related to alignin and ethanol plant.

FIG. 3 shows a schematic view of a continuous tube reactor related to ableached pulp mill.

FIG. 4 shows a conventional Kraft process.

FIG. 5 shows a sectional view of a tube reactor showing the inlet andextraction perforations that cooperate with the extraction rings.

FIG. 6 shows a plurality of extraction rings.

FIG. 7 shows fluid flow across a reactor tube at various porositylevels.

FIG. 8 shows the energy efficiency of continuous cooking versus batchcooking.

FIG. 9 shows a schematics view of a tube reactor.

FIG. 10 shows a side cross-sectional view of a positive displacementpumping system.

DETAILED DESCRIPTION

Disclosed embodiments illustrate aspects of a continuous tube reactor.In some embodiments, a continuous tube reactor 100 converts higher gradecellulosic feedstock (material) in a relatively continuous process tofermentable sugars for ethanol production, to relatively chemical freelignin for products conventionally made from fossil base material, andto pulp for paper making and other products. In some embodiments, acontinuous tube reactor converts lower grade cellulosic material intolignin and fermentable sugars.

In some embodiments, a continuous tube reactor may use a multi-stagechemical “cracking” process to split cellulosic feedstock into threecommercial end-products, fermentable sugars for ethanol production,lignin for plastics and other conventionally fossil-fuel-base products,and pulp for paper making. Additionally, this cracking process may beaccomplished with a single pressure vessel and may use existingauxiliary equipment. In this way, a continuous tube reactor may providetransformational harvesting and use of sustainable renewable cellulosicmaterials, transformational production of alternative fuels,transformational production of pure lignin and products thereof, andtransformational production of pulp, as will be described in more detailin the following detailed description with reference to the attachedfigures.

FIG. 1 shows an isometric view of one form of a digester. In someembodiments, a continuous tube reactor may comprise a continuous woodchip or other cellulosic material (feedstock) feed section, apre-steaming and impregnation section where air is removed and thefeedstock impregnated with mild acid solution, and the actual digestersections. In some embodiments all section of the continuous tube reactormay have a tubular shape.

With reference to the example embodiment illustrated in FIG. 1, an 8″diameter pilot-scale continuous tube reactor 100 may be about 110 ftlong and have 47 inlet/extraction rings. In contrast, conventional pulpdigesters have from 3 to 6 inlet/extraction rings. The additionalinlet/extraction rings allow a very accurate process control. Theembodiment in FIG. 1 shows a 24 ft long section consisting of second andthird cooking zones and an end wash zone in front at left, with a 21 ftlong section of a mild acid hydrolysis and first cooking zones behindit. Further behind these sections there are three twenty feet long tubesections that form 60 ft long chip feed, pre-steaming and impregnationsections. The cellulosic feedstock is processed in this embodimentpilot-scale tube reactor in a continuous manner.

In the present embodiment, all process auxiliary tanks, blow tank forpulp discharge, sugars and lignin concentrators, lignin recoverycentrifuge, air compressor, and vacuum evaporation equipment andcondensers for ethanol recycling are mounted on a 32 ft long goose-necktrailer. This allows a pilot-scale continuous tube scale reactor to betransported and re-assembled within a relatively short time, such as aweek or two from a pulp mill, saw mill or ethanol plant to another toallow multiple end-users to experiment with their own feedstock,laboratories, and in case of ethanol facilities, with their ownfermentation and distillation processes.

For high-grade woody cellulosic feedstock some embodiments of acontinuous tube reactor may have six process zones for unbleached pulp,including a zone to hydrolyze hemicelluloses to fermentable sugars andextract them, three cooking zones to dissolve and extract lignin inthree stages, a three-stage wash zone consisting of hot alcohol wash,hot water wash, and cold water wash, and a pulp discharge zone. In someembodiments, for bleached pulp production one or more bleaching zonesmay added between cooking zones and an end wash zone.

In one example embodiment, cellulosic material may be converted tofermentable sugars, lignin and pulp in one single pass through ahorizontal tubular pressure vessel using a solution comprising 60%ethanol and 40% water for a transportation and process liquid. Forexample, an embodiment process liquid may be a mixture of around 60%ethanol and 40% water at 350°-400° F. and a process pressure of 300psig. In this example, each of the process zones may have severalprocess liquid inlet/extraction rings to provide heat and process liquidinput and dissolved organic matter extraction as well as processconsistency and porosity control within the entire length of thereactor, as will be explained more fully in the following detaileddescription.

FIG. 2 shows a schematic view of an embodiment continuous tube reactor200 related to a lignin and ethanol plant. For low-grade woody 204 andany grassy 202 cellulosic feedstock for production of lignin 234 andethanol 248, as shown in FIG. 2, the continuous tube reactor 200 mayhave nine process zones. For example, continuous tube reactor 200 mayhave two zones to hydrolyze hemicelluloses to fermentable sugars andextract them as shown to the left of block 206 and in the middle ofblock 206, and two zones to hydrolyze cellulose to fermentable sugarsand extract them as shown in the sections of block 206 immediately tothe right of the hemicellulose hydrolization sections. Additionally,continuous tube reactor 200 may include four cooking zones to dissolveand extract lignin in four stages as shown in block 206, and a residualfibrous matter discharge zone as shown on the far right of block 206.

In the present embodiment continuous tube reactor 200, the continuoustube reactor will process almost all of the feedstock into lignin 234and fermentable sugars without any pulp production except that a smallpercentage of the feedstock is left at the end of the reactor in afibrous stage to facilitate a cross-flow extraction process of dissolvedsugars and lignin. In this way, part of the residual fibrous matter canbe recycled back to the reactor feed end, if desired, or all of it canbe burnt to produce steam 212 and power 220 for the plant. Some of theresidual fibrous matter has to be always burnt to get rid of theinorganic salts and ashes in the feedstock.

As can be seen in FIG. 2, the process ethanol may be recycled throughevaporation and condensation in a conventional manner. Additionally,ethanol may be burned in a bio-fuel boiler 210 with the residualblow-out matter will be made up by a corresponding amount from the freshethanol produced in a conventional manner by fermentation of the sugarsand distillation of the freshly produced ethanol. The dissolved purechemical free lignin 234 may then be recovered through evaporation,flash drying 230 and bag house 232 operation.

Organic vapors from evaporation and blow tank will be burned in aconventional bio-fuel boiler 210 as well as the organic extractives fromthe impregnation liquid. In this way, small amounts of fresh make-upwater may be used since much of the moisture in the feedstock can berecycled through evaporation, as shown in FIG. 2. Additionally, theacidity of the hydrolyzed sugar stream may be buffered with lime 224before fermentation 222.

FIG. 3 shows a schematic view of a continuous tube reactor 300 relatedto a bleached pulp mill FIG. 4 shows a conventional Kraft process 400.We now demonstrate a reduction in energy-related emissions includinggreenhouse gases by comparing the conventional modern Kraft process 400to the continuous tube reactor bleached pulp mill diagram in FIG. 3.

The continuous tube reactor 300 eliminates the recovery boiler 438,causticising 448 and lime kiln 452, which are generally responsible for¾ of the emissions and greenhouse gases of a Kraft process 400 mill. Inthis way, by combining the cooking, washing and bleaching processes intoone continuous process inside multiple, relatively small diametercontinuous tube reactors 300, all the process liquids may be circulatedcounter-currently upstream until being extracted to an evaporationplant, and the emissions and greenhouse gases may be dropped to lessthan 10% of a Kraft process 400 mill's values.

Additionally, a continuous tube reactor 300 uses very clean ethanol forcooking liquor instead of sodium and sulfur-containing Kraft process 400chemicals, further allowing for reduced evaporation plant emissions.Also, a Kraft process 400 mill operates by burning lignin and otherdissolved organic matter to recover costly cooking chemicals from ashesthrough causticising and lime kiln processes.

FIG. 5 shows a sectional view of a tube reactor showing the inlet andextraction perforations 502 that cooperate with the extraction rings506. FIGS. 5 and 6 relate to reducing the porosity of feedstock within atube reactor that may be used in either a continuous or a batch processand are utilized in continuous tube reactor 900 as illustrated anddescribed with reference to FIG. 9.

FIG. 6 shows a partial sectional view of plurality 600 of extractionrings 662, 664, etc. In FIG. 6, the fluid flow including feedstock isindicated by arrow 660 is to be passed through the tube reactor (notshown). In general, a tube reactor may be provided with openingstherearound to communicate with the various passageways and theplurality 600 of fluid transport rings.

With reference to FIG. 6 in detail, in the right-hand portion of FIG. 6is a fluid passage ring 662 which is a packing ring. As described above,when it is desired to lower the porosity of the feedstock at any pointalong the entire tube reactor assembly, a positive displacement pump (asshown in FIG. 10) or cylinder will release a known volume of fluidthrough a packing ring 662 while the main drive system of the entireunit is adding additional fluid to the entrance portion of a digester orcontinuous tube reactor. In other words, in a preferred form, thevarious fluid biasing members are positive displacement pumps orcylinders, and if one unit of water enters the digester at an entranceportion, a downstream packing ring can simultaneously extract one unitprocess liquid (volumetric unit), thereby controlling the compression ofthe feedstock at that particular location adjacent to that particularpacking ring.

As further shown in FIG. 6, an array of countercurrent displacementrings 664 may be utilized to extract dissolved organic matter from thefeedstock at various stages throughout the tube reactor process. Such adetailed description of one form of a countercurrent flow is describedin U.S. Pat. No. 5,680,995, which is incorporated by reference and is apatent invented by the same inventor of this application. One preferredmethod of passing fluid through countercurrent displacement rings 664will be described below with reference to FIG. 10.

FIG. 7 shows fluid flow across a reactor tube at various porositylevels. By way of illustration, if porosity (a measure of the voidspaces in a material as a fraction, between 0-1, or as percentagebetween 0-100%, typically 0.01 for solid granite to more than 0.5 forpeat and clay) is too high, a situation occurs as shown in the left-handportion 710 and 740 where a displacement washing may flow in anon-uniform manner across a pipe cross section. For example, withreference to 710, a displacement washing may flow from a typically 90degree open section at 6 o'clock to the typically 180 degree opensection at 12 o'clock, such that there is not a sufficient amount ofresistance to the flow and whereby the flow is not complete and nottraveling through the 4.30 to 3 and 7.30 to 9 o'clock lateral regions.Essentially, the fluid takes a tunnel flow approach and does not provideadequate coverage of the feedstock due to too high of porosity of thefeedstock.

Now looking at 720 and 750 in FIG. 7, it can be seen that there is alower porosity where the flow from 4.30 and 7.30 o'clock to 3 and 9o'clock is in somewhat more of a steady stratified manner where theacross-tube flow of the inlet displacing liquid is reaching the 3 and 9o'clock locations in a more evenly distributed fashion to extract thedisplaced liquid at the top. And now looking at 730 and 760, it can beseen that the even lower porosity has a much more even cross-flow stratavelocities to perform a more complete cross-sectional displacement ofthe fluid to be extracted.

Therefore, having a lower porosity is advantageous for displacing theliquid contained within the digester with new fresh liquid from oneperipheral location along the tube reactor. FIG. 8 shows the energyefficiency of continuous cooking versus batch cooking.

FIG. 9 shows a schematic view of a batch process embodiment of acontinuous tube reactor 900. In general, continuous tube reactor 900includes a pre-impregnation section 910, then a reactor section 950 andan end a washing section 980. The pre-impregnation section 910 in oneform can be filled up with feedstock, thereafter filled with water,where the leading plug 930 remains in place by fill water in thedownstream sections 950 and 980. A typical feedstock may be anycellulosic material, from woody materials to grasses, and other possiblefeed materials. After the feedstock is inserted, an end cap containing atrailing plug 932 may be fastened to the end of the tube 910.Thereafter, water may be placed in the section 910 to fill the voidspaces between feedstock particles. The trailing piston 932 has waterpressure or otherwise a biasing force placed thereon to bias it.

In one form, a biasing system include pumping water behind trailing plug932, whereby the pressure over the surface area creates a force whichpressurizes the water between the leading and trailing plugs. In thisway, leading piston 930 may remain intact as long as fill water in thereactor section 950 and washing section 980 is not relieved through arelief valve.

In the embodiment illustrated in FIG. 9, various openings are providedalong the tube 900, thereby allowing liquid to escape in a controlledmanner through positive displacement pumps or cylinders and leaving thefeedstock therein. In this way, the ratio of water to the raw feedstockmay be reduced, in turn lowering the feedstock porosity.

After the feedstock porosity is adjusted to a defined level, thefeedstock/water mixture may be heated to a temperature and thenpre-impregnated with a water and chemical solution. After a time theleading piston and all the feedstock material between the leading andtrailing plugs may then be allowed to travel forward by setting therelief valve at the end of the washing section 980 to relieve at adesired pressure. The speed of the travel of feedstock may be controlledby the water input volume per unit of time behind the trailing plug 932

There are four process zones in the reactor section 950 as shown inexample embodiment 900, with each process zone ending with apacking/extraction section. In general, the packing/extraction sectionhas a series of rings including an initial packing ring and severalsubsequent countercurrent displacement rings described further herein.At the beginning of the first process zone, named mild acid hydrolysiszone 956, the porosity of the feedstock is first lowered to a level byextracting some liquid out with a so-called packing ring. The volume ofextraction may be controlled by measuring it with a positivedisplacement pump or cylinder.

After the packing ring, the initial impregnation fluid may be extractedwith a mild acid hydrolysis liquid, such as an acid hydrolysis liquidcontaining 60% alcohol, 1% sulfuric acid, and 39% water, by way ofexample. The extraction may be accomplished by a measured amount of mildacid hydrolysis liquid being pumped into the last of the severaldisplacement rings with a positive displacement pump or cylinder. Insome embodiments, several of these pumps or cylinders may be “ganged” tooperate together so that the liquid that is displaced within the firstextraction ring will flow into the inlet side of the next pump orcylinder to be delivered to the second displacement ring and so on. Inthis manner the fresh ingoing liquid will counter-currently “wash” outthe liquid to be extracted; however, the porosity remains relativelyconstant throughout the entire extraction section since all input/outputliquid volumes are same by virtue of all displacement pumps or cylindersbeing of same volume.

This newly input mild acid hydrolysis liquid converts the feedstockhemicelluloses to sugars, which are then extracted in a similar mannerat the end of the process zone after a packing ring has first reducedthe porosity again by a desired value corresponding to the amount thatthe feedstock has shrunk during its travel through the processing zone.Again a packing ring may be followed by four or more displacement ringswhich in a countercurrent flow pattern extract the processed sugars to asugar concentrator tank to be further processed in a conventional mannerthrough fermentation to ethanol.

Some embodiments may utilize three subsequent process zones with theirown packing and extraction sections following the above sugar extractionsection. In these embodiments, these process zones may be a first ligninextraction zone, a second lignin extraction zone, and a third ligninextraction zone, and numbered 974, 942, and 978 respectively. In apreferred embodiment, the process liquid in these zones is 60% ethanoland 40% water.

After de-lignification, there may be an additional packing ring followedby a four-ring hot alcohol countercurrent displacement wash, anotherfour-ring counter-current hot water wash, and finally a four-ringcounter-current cold-water wash. Thereafter, a discharge section 988 maydischarge the feedstock to a blow tank utilizing the pressure within thesystem to bias the material outward.

With the foregoing description in place, there will now be a moredetailed discussion of lowering the porosity. In general, throughout thesystem, the porosity values may change given the various states of thefeedstock. As the feedstock is processed through the various zones itsparticle size and shape is reduced and the particles soften due to theorganic matter being dissolved from the feedstock. To avoid porosityincrease the feedstock may be packed at the end of each process zone tomaintain proper and uniform displacement liquid cross-flow.

In general, with each positive displacement piston within an embodiment,there may be a pressure drive system upstream of the system thatprovides sufficient pressure for passing the feedstock and theintermediate pistons through the tube reactor assembly. In order tocontrol the porosity in the manner described above, the feed drive mayprovide a certain displacement of a known quantity of fluid.

In an example embodiment, the feed drive is a positive displacementdevice which positively displaces a prescribed amount of fluid into thesystem. Along the way, various packing rings in the system controls theporosity through the entire tube reactor. Basically, in order to packthe feedstock and lower the porosity, the intermediate packing ringswill be extracting liquid at intermediate stages. In other words, at thevery end portion of the system there is a pressure-relief-valve-basedextraction whereby if (for example) one unit of water is pumped in bythe feed pump or cylinder behind the trailing plug and one unit of wateris removed at a packing ring, then the particles of the feedstock beforethat particular packing ring will move closer to one another (whereinthe trailing piston will advance forward), and effectively the porosityof the feedstock in that section is lowered.

FIG. 10 shows a side cross-sectional view of a positive displacementpumping system. As shown in FIG. 10 there is a positive displacementpumping assembly 1000. In general, the assembly is provided with acentral shaft 1002 that is operatively connected to a plurality of drivepistons 1004A-1004E (where—the drive pistons in sum will commonly bereferred to as the drive pistons 1004). The central shaft is furtherconnected to a drive piston 1006 which is powered by hydraulic fluidpassing through the valve assembly 1008. In general, the drive piston1006 applies a force to the central shaft 1002, which in turn biases theplurality of drive pistons 1004, which in turn bias fluid containedwithin the first and second chambers 1010 and 1012.

In this way, FIG. 10 shows the chambers 1010 and 1012 on either side ofthe drive piston 1004A, wherein each of these chambers are configured tointake fluid through an intake line 1014 through the check valves 1016and 1018. Further, the fluid within the chambers 1010 and 1012 isconfigured to be discharged through the output line 1020, which receivesfluid through either the check valves 1022 or 1024 depending upon whichdirection the drive piston 1004 is traveling in.

Therefore, referring now back to FIG. 6, it can generally be appreciatedthat the pump assembly 1000 can be connected to the various cross-flowrings for distributing fluid therethrough. For example, the firstcross-flow ring in the array will pass fluid from the pump assembly thathas already been processed through the forward process rings in acountercurrent flow-like manner as described in detail in U.S. Pat. No.5,680,995.

However, the pump assembly provides operation of multiple drive pistonsin a positive displacement manner that inject and withdraw a prescribedamount of fluid to maintain the fluid content within the system. Fluidcan thus be extracted at prescribed intervals based on either gauges orknown properties of the feedstock to adjust the porosity as describedabove. In general, a pump assembly having, for example, a single pistoncan be utilized for extracting fluid from a packing ring 662 as shown inFIG. 6. As shown in FIG. 10, the pump assembly 1000 has the additionalfeature of extracting injecting fluid simultaneously by having thesubstantial simultaneous movement of the drive pistons 1004, which areall commonly connected to the central shaft 1002.

It will further be understood that the configurations and/or approachesdescribed herein are exemplary in nature, and that these specificembodiments or examples are not to be considered in a limiting sense,because numerous variations are possible. The specific routines ormethods described herein may represent one or more of any number ofprocessing strategies. As such, various acts illustrated may beperformed in the sequence illustrated, in other sequences, in parallel,or in some cases omitted. Likewise, the order of any of theabove-described processes is not necessarily required to achieve thefeatures and/or results of the embodiments described herein, but isprovided for ease of illustration and description.

The subject matter of the present disclosure includes all novel andnonobvious combinations and subcombinations of the various processes,systems and configurations, and other features, functions, acts, and/orproperties disclosed herein, as well as any and all equivalents thereof.

1. A continuous digester comprising: a cellulosic material feed sectionincluding a pre-steam and impregnation zone, the pre-steam andimpregnation zone to remove air from cellulosic material and toimpregnate the cellulosic material with a mild acid solution; a sugarextraction zone coupled with the pre-steam and impregnation zone, thesugar extraction zone to hydrolyze hemicellulose in the cellulosicmaterial to fermentable sugars and extract the fermentable sugars; acooking zone to receive the cellulosic material from the sugarextraction zone, the cooking zone to dissolve the cellulosic materialand extract lignin; a end wash zone consisting of a hot alcohol wash, ahot water wash, and a cold water wash, the end wash zone to wash thecellulosic material and discharge pulp.
 2. The continuous digester ofclaim 1, wherein the sugar extraction zone further includes a packingring to extract liquid from the cellulosic material and lower theporosity of the cellulosic material in the sugar extraction zone.
 3. Thecontinuous digester of claim 2, further comprising a positivedisplacement pump in fluid communication with the packing ring, thepositive displacement pump to adjust the amount of liquid extracted bythe packing ring.
 4. The continuous digester of claim 1, wherein thecooking zone further includes at least one packing ring to extractliquid from the cellulosic material and lower the porosity of thecellulosic material in the cooking zone.
 5. The continuous digester ofclaim 4, wherein the packing ring is further in fluid communication witha positive displacement pump, the positive displacement pump to adjustthe amount of liquid extracted by the packing ring.
 6. The continuousdigester of claim 5, wherein the cooking zone is a first cooking zone,the continuous digester further comprising at least one additionalcooking zone to dissolve cellulosic material and extract lignin.
 7. Thecontinuous digester of claim 1, further comprising at least one bleachzone between a last cooking zone and the end wash zone, the bleach zoneto bleach the cellulosic material and the continuous digester todischarge bleached pulp.
 8. A method comprising: receiving cellulosicmaterial in a continuous digester; removing air from the cellulosicmaterial; impregnating the cellulosic material with a mild acid;hydrolyzing hemicellulose in the cellulosic material to fermentablesugars; extracting the fermentable sugars from the cellulosic material;cooking the cellulosic material to extract lignin from the cellulosicmaterial; washing the cellulosic material in a hot alcohol wash, a hotwater wash, and a cold water wash; and discharging pulp.
 9. The methodof claim 8, further comprising extracting liquid from the cellulosicmaterial in the sugar extraction zone using a packing ring to lower theporosity of the cellulosic material.
 10. The method of claim 9, furthercomprising adjusting the amount of liquid extracted by the packing ringwith a positive displacement pump in fluid communication with thepacking ring.
 11. The method of claim 8, further comprising extractingliquid from the cellulosic material in the cooking zone using a packingring to lower the porosity of the cellulosic material.
 12. The method ofclaim 11, further comprising adjusting the amount of liquid extracted bythe packing ring with a positive displacement pump in fluidcommunication with the packing ring.
 13. The method of claim 8, furthercomprising: bleaching the cellulosic material after cooking and prior towashing; and discharging bleached pulp.